3.1 Which Came First: The End of Drought or the Beginning of Flood (in Texas in 2015)?

Tuesday, 12 January 2016: 1:30 PM
Room 338/339 ( New Orleans Ernest N. Morial Convention Center)
John Nielsen-Gammon, Texas A&M Univ., College Station, TX

Handout (39.9 MB)

The drought of 2010-2015 in Texas was the second-worst drought on record. By the final months of the drought, the primary remaining impacts were low reservoir and aquifer levels, which persisted in many areas despite the presence of near-normal rainfall in most watersheds. Then came May 2015, the wettest month on record by far, and records were also set for wettest two months, wettest three months, wettest four months, and wettest first half of the year. Total rainfall across the state averaged over 9", and such an event in any of the wetter months of the year has an estimated return period of 500-1000 years. Most reservoirs recovered very quickly, with some going from 20% of capacity to 100% of capacity in less than two weeks. There was a strong apparent influence by El Niņo in the large-scale conditions that permitted the extended period of rainy weather. The effect of climate change on the overall monthlong conditions is unclear, including the sign of the effect, while the more direct thermodynamic effect on the water vapor carrying capacity of the atmosphere likely had a direct rainfall-enhancing effect on the individual flash flood episodes within the wet month. The interaction of climate change and El Niņo has parallels to a faucet, whereby climate change enlarges the pipe while ENSO controls the handle.
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